TRANSFORMERS
Transformers are devices that are able to change the size of the _______ and consequently the size of the
______ of __.C. electricity.
They are able to do this by using the __________ Currents to create changing ______ fields in the iron
core at the centre of a coil of wire that has a known number of coils.
This, the first coil the electrical energy passes through, is called the ______ coil .
These changing magnetic fields are carried through the ____ core, and these fields then spring in and out
of the iron core to cut another ____ of ____ with a different number of coils than the first.
This second coil that the electrical energy passes through is called the _________ coil. As the changing
________ field lines cut through the _________ coil they create changing ________. The more coils there
are in the secondary, the more ________ that is created by the field lines cutting through them.
ALTHOUGH THE VOLTAGE MAY INCREASE, _______ CANNOT BE CREATED NOR
DESTROYED AND SO THE_______ MUST DECREASE TO KEEP
THE POWER IN AND THE POWER OUT THE SAME.
THIS MEANS TRANSFORMERS ARE (ALMOST) ____% EFFICIENT.
iron core
IP
VP
VS = NS = IP
VP NP IS
IS
NP
NS
VS
POWER OUT = POWER IN
VS x IS = VP x IP
Where VS is the ………………………………………………..
Vp is the ………………………………………………..
IS is the ………………………………………………..
IP is the ………………………………………………..
NS is the ………………………………………………..
NP is the ………………………………………………..
The ratio of coils is the same as the ratio of _________, and the inverse of the ratio of __________.
If the voltage increases it is a STEP ____ transformer. If the voltage decreases it is a STEP ____.
NP
NS
Vp
IP
100
2500
1000
500
200V
3000V
6A
1A
200
2000
50 000V
10000
POWER IN
x
VS
IS
=
5A
5000W
250A
200mA 2MW
Where would you find the step up transformers?
Where would you find the step down transformers?
POWER OUT
x =
1000V
200V
4000V
10A
10 000W
30A
Up/Down?